Prepare the beef barbacoa according to your recipe. Separate sauce and blend in blender. Set aside.
Mix enchilada sauce with 1/2 cup (or more) of the barbacoa sauce.
Preheat the over to 350F. Coat the bottom of a 9 x 13" casserole dish with a thin layer of the mixed enchilada sauce.
Over medium-high heat, saute yellow squash, corn, and shredded beef until squash is cooked and the mixture warmed through. Remove mixture with a slotted spoon and set aside, leaving the remaining liquid in pan. To the mixture, add 1 cup of shredded cheese and stir to combine.
Add water or extra sauce to the a small amount of the enchilada sauce left in the pan. Using tongs and working one at a time, slip the tortillas into the saucepan to cover both sides with sauce.
Once coated, add up to up to 1/2 cup of the mixture to each tortilla and arrange in dish. This will depend on the size of your tortillas, cooking vessel, and your preference for the amount of filling, so adjust to your own liking. People here like huge burrito-type enchiladas.
Pour remaining enchilada sauce over the tortillas and top with remaining cheese.
Bake uncovered for 20 minutes, or until everything is hot and the cheese is melted.